Proper motions of field L and T dwarfs - II

S L Casewell,M R Burleigh,R F Jameson

doi:10.1111/j.1365-2966.2008.13855.x

S L Casewell, M R Burleigh + Show 1 more

Open Access

https://doi.org/10.1111/j.1365-2966.2008.13855.x

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Abstract

By using images taken with Wide Field Camera (WFCAM) on United Kingdom Infrared Telescope (UKIRT) and Son of ISAAC (SofI) on the New Technology Telescope (NTT) and combining them with Two Micron All Sky Survey (2MASS) we have measured proper motions for 126 L and T dwarfs in the dwarf archive. Two of these L dwarfs appear to have M dwarf common proper motion companions, and two also appear to be high-velocity dwarfs, indicating possible membership of the thick disc. We have also compared the motion of these 126 objects to that of numerous moving groups, and have identified new members of the Hyades, Ursa Major and Pleiades moving groups. These new objects, as well as those identified in Jameson et al. have allowed us to refine the L dwarf sequence for Ursa Major that was defined by Jameson et al.

Highlights

Brown dwarfs may be thought of as failed stars
The majority of the brown dwarfs that have been discovered to date are field objects found using surveys such as the Two Micron All Sky Survey (2MASS; Skrutskie et al 2006, see Leggett et al 2002 for examples), the DEep Near-Infrared Sky survey (DENIS; DENIS Consortium 2005, see Delfosse et al, 1999 for examples), the Sloan Digital Sky Survey (SDSS;York et al 2000 see Hawley et al 2002 for examples) and the United Kingdom Infrared Telescope (UKIRT) Deep Infrared Sky Survey (UKIDSS; Lawrence et al 2007, see Kendall et al 2007; Lodieu et al 2007a for examples)
This paper continues the work presented in Jameson et al (2008a), which presented proper motions of 143 L and T dwarfs

Summary

INTRODUCTION

Brown dwarfs may be thought of as failed stars. These low mass ( 70 MJup Burrows et al 2001), cool objects are the lowest mass objects that the star formation process can produce. To continue the study started by Bannister & Jameson (2007) and Jameson et al (2008a), we have measured proper motions for the majority of the remaining known field L dwarfs listed in the online L and T dwarf archive (http://spider.ipac.caltech.edu/staff/davy/ARCHIVE/) This has again been accomplished using the WFCAM on UKIRT and for the more southern objects, Son of ISAAC (SofI) on the 3.58m ESO New Technology Telescope (NTT). Using these wide field images and existing catalogue data, we have measured proper motions for an additional 126 L and T dwarfs listed in the dwarf archive.

Data acquisition and reduction

Calculating proper motions

CONCLUSIONS